Domestic animals such as sheep and cattle are generally marked in some manner to allow the animal to be identified. Traditionally, cattle have been branded by a hot iron. This method is time-consuming and brands are subject to wear, damage or alteration. Ear tagging is another commonly used method. However, tags are often lost or damaged during the lifetime of the animal. They are also not security proof and may be replaced or altered by a third party.
More recently, microchips have been implanted under the animal's skin, normally behind the ear. A disadvantage of this system is that the microchip may contaminate food products obtained from the slaughtered animal. Further, implantation must normally be conducted by a suitably skilled person.
A further proposal for identifying animals has been described in Australian Patent No. 649,212. This patent describes a device having a ceramic housing with a transponder located therein. The capsule is administered by mouth and settles in the stomach. The housing is sealed by a cap. The cap is magnetic to allow post-slaughter location of the device.
One disadvantage of the ceramic capsules is that they are relatively time-consuming and costly to manufacture. First, the ceramic housing must be prepared by conventional ceramic techniques such as shaping a powder, mixing and sintering at high temperatures. The transponder is then placed inside the capsule and in a further step the capsule is sealed by the cap. Alternatively, the transponder may be glued to the ceramic capsule. In either case, it is possible for the cap or the transponder to become dislodged from the capsule. Once dislodged, they are subject to loss from the animal.
Further, in order for the capsule to remain a viable means of identifying the animal it must remain in the stomach for an extended period and preferably for the lifetime of the animal. Capsules may be lost through regurgitation or may be passed from the animal. It has been found that the ceramic capsules as described in Australian Patent No. 649,212 may be lost in this manner.